1. Technical Field - Field of the Invention
The present invention pertains to random access disk storage systems, and in particular, to system for continuous application of a lubricant to the surface of a magnetic storage disk to facilitate non-destructive start and operation of a flying head or slider.
2. Description of the Prior Art
The density of magnetic recording is inversely related to the height of the magnetic transducer above the disk surface. As a general proposition, increased storage capacity is obtainable by flying the heads closer to the disk surface. As the heads approach very closely, some contact with the disk surface is inevitable. This is particularly the case during the period of time while the disk is being brought up to operating speed and to a stop.
Lubricants have been applied to the disk surface as a part of the manufacturing process. This technique, although presenting contamination problems and potential loss of lubricant due to spin-off, has been generally adequate to satisfy requirements for prior art systems. However, as the head-disk spacing decreases and the application of lubricant is applied only during the manufacturing process is inadequate to ensure reliable performance over the life of the disk file.
The continuous application of a lubricant to the surface of the disk has been known since almost the very beginning of disk file development. For example, U.S. Pat. No. 2,969,435 "Oil Film Spacer for Magnetic Recording Device" to Lynott, issued Jan. 24, 1961, and assigned to the assignee of the present invention, shows a magnetic transducer having an oil discharge port located ahead of the flying surface of the transducer. Oil is pumped through the port to coat the surface of the disk and provide a lubricating film on which the transducer rides.
The lubrication requirements for near contact recording devices necessitates the use of a low viscosity lubricant to permit the requisite close approach of the slider to the disk surface. A low viscosity lubricant will drain away from the disk over time, and also migrate to the coolest spot in the disk drive enclosure, as a result of evaporation and condensation, which spot will be likely to be somewhere on the cover and not on the desired disk location. Because of the lubricant movement away from the point where it is needed, the lubricant dispenser must be very near the slider in the start/stop zone when the disk storage system is at rest. The main concern is lubrication under the head at the instant of start up.
Various systems for transporting the lubricant to the desired location near the slider have been considered, beginning with the pressurized reservoir and feed approach taught by the Lynott patent. Unfortunately, the complexity and resulting cost of the pressurized feed approach make it an altogether unsatisfactory approach to the current problem and alternatives have been sought. Ideally, the lubrication delivery system would not require additional power in the form of a pump. The system should not require a sequencing delay in start up to accommodate lubricant flow prior to initiating rotation. The delivery system should provide an adequate supply of lubricant from the very outset of startup.
It has been recognized that the use of a wick to convey the surface lubricant to the slider is an approach which overcomes many of the difficulties associated with other approaches. However, to adequately supply the lubricant, particularly at startup, the wick would have to be in intimate contact with the disk. Use of an applicator in intimate contact with a disk introduces contaminants to the lubricant and also adds to the complexity of the overall mechanical actuator system as the applicator has to move with the slider. This is obviously not a practical solution since such a design would be very complicated and, at best, completely subvert the very sophisticated slider suspension system.